The field test for the optimal operation of electric hot water storage tanks (WWS) shows the practical application of the optimisation routines and mathematical models developed in FZE for system identification and condition determination. 16 household MMS were equipped with simple and retrofittable measurement, regulation and control technology, which determines and carries out the optimum heating times for the following day on the basis of a cost function. In addition, the quantity and time of the expected hot water demand, system capacity and power loss are independently determined and taken into account in the optimisation, thus increasing the efficiency of the MMS. The entire data processing (storage and optimisation) takes place locally in the household. This preserves the privacy of the residents and prevents access from outside.

Project Results

Initial results from the field test show that there is in some cases considerable potential for savings both in terms of the stock market price (an example of the cost function) and in terms of energy consumption (which is reflected in the storage losses). Energy savings in the range of 35% and cost reductions (exchange price) of more than 30% are possible for 1/3 of the MMS. Apportioned to 1/3 of the MMS installed in Vorarlberg (approx. 90,000 in total), this would represent energy savings of approx. 7,000 MWh.

We would like to thank the participating households for their confidence in us and for the possibility to carry out this field test.

The development of the hardware and the retrofitting of the storage tanks was still carried out within the FFG project Smart City Rheintal ( The algorithms used were partly developed within the Josef-Ressel Centre for Applied Scientific Computing in Energy, Finance and Logistics (

Contact persons Research Centre Energy

Prof. (FH) Dr.-Ing. Markus Preißinger
illwerke vkw Endowed Professorship for Energy Efficiency, Head of the Research, Head of the Research Center Energy

+43 5572 792 3801

V7 20


DI Helena Gössler

+43 5572 792 3800

V7 21


Further research projects by the research centre Energy